Arcgis server on https

Hi - I have a flex viewer which accesses a secured map service at a third party site. The service is published on https and throws up a username and password before I can access it. The publishers of the service would prefer not to allow https request headers in their crossdomain file so we have had to publish our viewer on https.

Anyway that is working now to view the service, but I cannot get the print service to work. The response from the gp service is {"error":{"code":400,"message":"Unable to complete operation.","details":["Error executing tool."]}}. The arcgisserver log is not much more helpful.

I have tried securing the print service in ArcGIS Server Manager on our server but got the same error.